The use of elastomeric or plastic material for vehicle fuel tanks has advantages over metal tanks. Such tanks can be readily manufactured by the inexpensive blow molding technique. However, some plastic fuel tanks that have a large bottom surface may exhibit support problems. With some fuel tank configurations and in some vehicles, only two support straps can be used to secure the tank to the vehicle structure. These straps may have to be placed at a relatively wide spacing interval. Between these straps, the weight of the fuel and internal pressures tend to cause the tank bottom to sag.
There have been previous attempts to reinforce walls of fuel tanks. For example, U.S. Pat. No. 3,406,855 to McKechnie discloses a liquid tank with metal reinforcement members attached thereto by fasteners. U.S. Pat. No. 3,335,903 to Anderson discloses a plastic tank with reinforcement ribs molded in the walls of the tank. U.S. Pat. No. 4,609,120 to Lauer discloses a plastic container with channels formed in the bottom to receive V-shaped members which are slid in from open ends of the groove.
U.S. Pat. Nos. 3,330,439 and 4,518,091 to Moorman and Scheurenbrand disclose fuel tanks with elongated recesses molded or stamped in the surface of the walls for imparting strength to the walls.